uIP 1.0: apps/resolv/resolv.c Source File

00001 /**
+00002  * \addtogroup apps
+00003  * @{
+00004  */
+00005 
+00006 /**
+00007  * \defgroup resolv DNS resolver
+00008  * @{
+00009  *
+00010  * The uIP DNS resolver functions are used to lookup a hostname and
+00011  * map it to a numerical IP address. It maintains a list of resolved
+00012  * hostnames that can be queried with the resolv_lookup()
+00013  * function. New hostnames can be resolved using the resolv_query()
+00014  * function.
+00015  *
+00016  * When a hostname has been resolved (or found to be non-existant),
+00017  * the resolver code calls a callback function called resolv_found()
+00018  * that must be implemented by the module that uses the resolver.
+00019  */
+00020 
+00021 /**
+00022  * \file
+00023  * DNS host name to IP address resolver.
+00024  * \author Adam Dunkels <adam@dunkels.com>
+00025  *
+00026  * This file implements a DNS host name to IP address resolver.
+00027  */
+00028 
+00029 /*
+00030  * Copyright (c) 2002-2003, Adam Dunkels.
+00031  * All rights reserved.
+00032  *
+00033  * Redistribution and use in source and binary forms, with or without
+00034  * modification, are permitted provided that the following conditions
+00035  * are met:
+00036  * 1. Redistributions of source code must retain the above copyright
+00037  *    notice, this list of conditions and the following disclaimer.
+00038  * 2. Redistributions in binary form must reproduce the above copyright
+00039  *    notice, this list of conditions and the following disclaimer in the
+00040  *    documentation and/or other materials provided with the distribution.
+00041  * 3. The name of the author may not be used to endorse or promote
+00042  *    products derived from this software without specific prior
+00043  *    written permission.
+00044  *
+00045  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
+00046  * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+00047  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+00048  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
+00049  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+00050  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
+00051  * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+00052  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+00053  * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+00054  * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+00055  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+00056  *
+00057  * This file is part of the uIP TCP/IP stack.
+00058  *
+00059  * $Id: resolv.c,v 1.5 2006/06/11 21:46:37 adam Exp $
+00060  *
+00061  */
+00062 
+00063 #include "resolv.h"
+00064 #include "uip.h"
+00065 
+00066 #include <string.h>
+00067 
+00068 #ifndef NULL
+00069 #define NULL (void *)0
+00070 #endif /* NULL */
+00071 
+00072 /** \internal The maximum number of retries when asking for a name. */
+00073 #define MAX_RETRIES 8
+00074 
+00075 /** \internal The DNS message header. */
+00076 struct dns_hdr {
+00077   u16_t id;
+00078   u8_t flags1, flags2;
+00079 #define DNS_FLAG1_RESPONSE        0x80
+00080 #define DNS_FLAG1_OPCODE_STATUS   0x10
+00081 #define DNS_FLAG1_OPCODE_INVERSE  0x08
+00082 #define DNS_FLAG1_OPCODE_STANDARD 0x00
+00083 #define DNS_FLAG1_AUTHORATIVE     0x04
+00084 #define DNS_FLAG1_TRUNC           0x02
+00085 #define DNS_FLAG1_RD              0x01
+00086 #define DNS_FLAG2_RA              0x80
+00087 #define DNS_FLAG2_ERR_MASK        0x0f
+00088 #define DNS_FLAG2_ERR_NONE        0x00
+00089 #define DNS_FLAG2_ERR_NAME        0x03
+00090   u16_t numquestions;
+00091   u16_t numanswers;
+00092   u16_t numauthrr;
+00093   u16_t numextrarr;
+00094 };
+00095 
+00096 /** \internal The DNS answer message structure. */
+00097 struct dns_answer {
+00098   /* DNS answer record starts with either a domain name or a pointer
+00099      to a name already present somewhere in the packet. */
+00100   u16_t type;
+00101   u16_t class;
+00102   u16_t ttl[2];
+00103   u16_t len;
+00104   uip_ipaddr_t ipaddr;
+00105 };
+00106 
+00107 struct namemap {
+00108 #define STATE_UNUSED 0
+00109 #define STATE_NEW    1
+00110 #define STATE_ASKING 2
+00111 #define STATE_DONE   3
+00112 #define STATE_ERROR  4
+00113   u8_t state;
+00114   u8_t tmr;
+00115   u8_t retries;
+00116   u8_t seqno;
+00117   u8_t err;
+00118   char name[32];
+00119   uip_ipaddr_t ipaddr;
+00120 };
+00121 
+00122 #ifndef UIP_CONF_RESOLV_ENTRIES
+00123 #define RESOLV_ENTRIES 4
+00124 #else /* UIP_CONF_RESOLV_ENTRIES */
+00125 #define RESOLV_ENTRIES UIP_CONF_RESOLV_ENTRIES
+00126 #endif /* UIP_CONF_RESOLV_ENTRIES */
+00127 
+00128 
+00129 static struct namemap names[RESOLV_ENTRIES];
+00130 
+00131 static u8_t seqno;
+00132 
+00133 static struct uip_udp_conn *resolv_conn = NULL;
+00134 
+00135 
+00136 /*---------------------------------------------------------------------------*/
+00137 /** \internal
+00138  * Walk through a compact encoded DNS name and return the end of it.
+00139  *
+00140  * \return The end of the name.
+00141  */
+00142 /*---------------------------------------------------------------------------*/
+00143 static unsigned char *
+00144 parse_name(unsigned char *query)
+00145 {
+00146   unsigned char n;
+00147 
+00148   do {
+00149     n = *query++;
+00150     
+00151     while(n > 0) {
+00152       /*      printf("%c", *query);*/
+00153       ++query;
+00154       --n;
+00155     };
+00156     /*    printf(".");*/
+00157   } while(*query != 0);
+00158   /*  printf("\n");*/
+00159   return query + 1;
+00160 }
+00161 /*---------------------------------------------------------------------------*/
+00162 /** \internal
+00163  * Runs through the list of names to see if there are any that have
+00164  * not yet been queried and, if so, sends out a query.
+00165  */
+00166 /*---------------------------------------------------------------------------*/
+00167 static void
+00168 check_entries(void)
+00169 {
+00170   register struct dns_hdr *hdr;
+00171   char *query, *nptr, *nameptr;
+00172   static u8_t i;
+00173   static u8_t n;
+00174   register struct namemap *namemapptr;
+00175   
+00176   for(i = 0; i < RESOLV_ENTRIES; ++i) {
+00177     namemapptr = &names[i];
+00178     if(namemapptr->state == STATE_NEW ||
+00179        namemapptr->state == STATE_ASKING) {
+00180       if(namemapptr->state == STATE_ASKING) {
+00181         if(--namemapptr->tmr == 0) {
+00182           if(++namemapptr->retries == MAX_RETRIES) {
+00183             namemapptr->state = STATE_ERROR;
+00184             resolv_found(namemapptr->name, NULL);
+00185             continue;
+00186           }
+00187           namemapptr->tmr = namemapptr->retries;
+00188         } else {
+00189           /*      printf("Timer %d\n", namemapptr->tmr);*/
+00190           /* Its timer has not run out, so we move on to next
+00191              entry. */
+00192           continue;
+00193         }
+00194       } else {
+00195         namemapptr->state = STATE_ASKING;
+00196         namemapptr->tmr = 1;
+00197         namemapptr->retries = 0;
+00198       }
+00199       hdr = (struct dns_hdr *)uip_appdata;
+00200       memset(hdr, 0, sizeof(struct dns_hdr));
+00201       hdr->id = htons(i);
+00202       hdr->flags1 = DNS_FLAG1_RD;
+00203       hdr->numquestions = HTONS(1);
+00204       query = (char *)uip_appdata + 12;
+00205       nameptr = namemapptr->name;
+00206       --nameptr;
+00207       /* Convert hostname into suitable query format. */
+00208       do {
+00209         ++nameptr;
+00210         nptr = query;
+00211         ++query;
+00212         for(n = 0; *nameptr != '.' && *nameptr != 0; ++nameptr) {
+00213           *query = *nameptr;
+00214           ++query;
+00215           ++n;
+00216         }
+00217         *nptr = n;
+00218       } while(*nameptr != 0);
+00219       {
+00220         static unsigned char endquery[] =
+00221           {0,0,1,0,1};
+00222         memcpy(query, endquery, 5);
+00223       }
+00224       uip_udp_send((unsigned char)(query + 5 - (char *)uip_appdata));
+00225       break;
+00226     }
+00227   }
+00228 }
+00229 /*---------------------------------------------------------------------------*/
+00230 /** \internal
+00231  * Called when new UDP data arrives.
+00232  */
+00233 /*---------------------------------------------------------------------------*/
+00234 static void
+00235 newdata(void)
+00236 {
+00237   char *nameptr;
+00238   struct dns_answer *ans;
+00239   struct dns_hdr *hdr;
+00240   static u8_t nquestions, nanswers;
+00241   static u8_t i;
+00242   register struct namemap *namemapptr;
+00243   
+00244   hdr = (struct dns_hdr *)uip_appdata;
+00245   /*  printf("ID %d\n", htons(hdr->id));
+00246       printf("Query %d\n", hdr->flags1 & DNS_FLAG1_RESPONSE);
+00247       printf("Error %d\n", hdr->flags2 & DNS_FLAG2_ERR_MASK);
+00248       printf("Num questions %d, answers %d, authrr %d, extrarr %d\n",
+00249       htons(hdr->numquestions),
+00250       htons(hdr->numanswers),
+00251       htons(hdr->numauthrr),
+00252       htons(hdr->numextrarr));
+00253   */
+00254 
+00255   /* The ID in the DNS header should be our entry into the name
+00256      table. */
+00257   i = htons(hdr->id);
+00258   namemapptr = &names[i];
+00259   if(i < RESOLV_ENTRIES &&
+00260      namemapptr->state == STATE_ASKING) {
+00261 
+00262     /* This entry is now finished. */
+00263     namemapptr->state = STATE_DONE;
+00264     namemapptr->err = hdr->flags2 & DNS_FLAG2_ERR_MASK;
+00265 
+00266     /* Check for error. If so, call callback to inform. */
+00267     if(namemapptr->err != 0) {
+00268       namemapptr->state = STATE_ERROR;
+00269       resolv_found(namemapptr->name, NULL);
+00270       return;
+00271     }
+00272 
+00273     /* We only care about the question(s) and the answers. The authrr
+00274        and the extrarr are simply discarded. */
+00275     nquestions = htons(hdr->numquestions);
+00276     nanswers = htons(hdr->numanswers);
+00277 
+00278     /* Skip the name in the question. XXX: This should really be
+00279        checked agains the name in the question, to be sure that they
+00280        match. */
+00281     nameptr = parse_name((char *)uip_appdata + 12) + 4;
+00282 
+00283     while(nanswers > 0) {
+00284       /* The first byte in the answer resource record determines if it
+00285          is a compressed record or a normal one. */
+00286       if(*nameptr & 0xc0) {
+00287         /* Compressed name. */
+00288         nameptr +=2;
+00289         /*      printf("Compressed anwser\n");*/
+00290       } else {
+00291         /* Not compressed name. */
+00292         nameptr = parse_name((char *)nameptr);
+00293       }
+00294 
+00295       ans = (struct dns_answer *)nameptr;
+00296       /*      printf("Answer: type %x, class %x, ttl %x, length %x\n",
+00297              htons(ans->type), htons(ans->class), (htons(ans->ttl[0])
+00298              << 16) | htons(ans->ttl[1]), htons(ans->len));*/
+00299 
+00300       /* Check for IP address type and Internet class. Others are
+00301          discarded. */
+00302       if(ans->type == HTONS(1) &&
+00303          ans->class == HTONS(1) &&
+00304          ans->len == HTONS(4)) {
+00305         /*      printf("IP address %d.%d.%d.%d\n",
+00306                htons(ans->ipaddr[0]) >> 8,
+00307                htons(ans->ipaddr[0]) & 0xff,
+00308                htons(ans->ipaddr[1]) >> 8,
+00309                htons(ans->ipaddr[1]) & 0xff);*/
+00310         /* XXX: we should really check that this IP address is the one
+00311            we want. */
+00312         namemapptr->ipaddr[0] = ans->ipaddr[0];
+00313         namemapptr->ipaddr[1] = ans->ipaddr[1];
+00314         
+00315         resolv_found(namemapptr->name, namemapptr->ipaddr);
+00316         return;
+00317       } else {
+00318         nameptr = nameptr + 10 + htons(ans->len);
+00319       }
+00320       --nanswers;
+00321     }
+00322   }
+00323 
+00324 }
+00325 /*---------------------------------------------------------------------------*/
+00326 /** \internal
+00327  * The main UDP function.
+00328  */
+00329 /*---------------------------------------------------------------------------*/
+00330 void
+00331 resolv_appcall(void)
+00332 {
+00333   if(uip_udp_conn->rport == HTONS(53)) {
+00334     if(uip_poll()) {
+00335       check_entries();
+00336     }
+00337     if(uip_newdata()) {
+00338       newdata();
+00339     }
+00340   }
+00341 }
+00342 /*---------------------------------------------------------------------------*/
+00343 /**
+00344  * Queues a name so that a question for the name will be sent out.
+00345  *
+00346  * \param name The hostname that is to be queried.
+00347  */
+00348 /*---------------------------------------------------------------------------*/
+00349 void
+00350 resolv_query(char *name)
+00351 {
+00352   static u8_t i;
+00353   static u8_t lseq, lseqi;
+00354   register struct namemap *nameptr;
+00355       
+00356   lseq = lseqi = 0;
+00357   
+00358   for(i = 0; i < RESOLV_ENTRIES; ++i) {
+00359     nameptr = &names[i];
+00360     if(nameptr->state == STATE_UNUSED) {
+00361       break;
+00362     }
+00363     if(seqno - nameptr->seqno > lseq) {
+00364       lseq = seqno - nameptr->seqno;
+00365       lseqi = i;
+00366     }
+00367   }
+00368 
+00369   if(i == RESOLV_ENTRIES) {
+00370     i = lseqi;
+00371     nameptr = &names[i];
+00372   }
+00373 
+00374   /*  printf("Using entry %d\n", i);*/
+00375 
+00376   strcpy(nameptr->name, name);
+00377   nameptr->state = STATE_NEW;
+00378   nameptr->seqno = seqno;
+00379   ++seqno;
+00380 }
+00381 /*---------------------------------------------------------------------------*/
+00382 /**
+00383  * Look up a hostname in the array of known hostnames.
+00384  *
+00385  * \note This function only looks in the internal array of known
+00386  * hostnames, it does not send out a query for the hostname if none
+00387  * was found. The function resolv_query() can be used to send a query
+00388  * for a hostname.
+00389  *
+00390  * \return A pointer to a 4-byte representation of the hostname's IP
+00391  * address, or NULL if the hostname was not found in the array of
+00392  * hostnames.
+00393  */
+00394 /*---------------------------------------------------------------------------*/
+00395 u16_t *
+00396 resolv_lookup(char *name)
+00397 {
+00398   static u8_t i;
+00399   struct namemap *nameptr;
+00400   
+00401   /* Walk through the list to see if the name is in there. If it is
+00402      not, we return NULL. */
+00403   for(i = 0; i < RESOLV_ENTRIES; ++i) {
+00404     nameptr = &names[i];
+00405     if(nameptr->state == STATE_DONE &&
+00406        strcmp(name, nameptr->name) == 0) {
+00407       return nameptr->ipaddr;
+00408     }
+00409   }
+00410   return NULL;
+00411 }
+00412 /*---------------------------------------------------------------------------*/
+00413 /**
+00414  * Obtain the currently configured DNS server.
+00415  *
+00416  * \return A pointer to a 4-byte representation of the IP address of
+00417  * the currently configured DNS server or NULL if no DNS server has
+00418  * been configured.
+00419  */
+00420 /*---------------------------------------------------------------------------*/
+00421 u16_t *
+00422 resolv_getserver(void)
+00423 {
+00424   if(resolv_conn == NULL) {
+00425     return NULL;
+00426   }
+00427   return resolv_conn->ripaddr;
+00428 }
+00429 /*---------------------------------------------------------------------------*/
+00430 /**
+00431  * Configure which DNS server to use for queries.
+00432  *
+00433  * \param dnsserver A pointer to a 4-byte representation of the IP
+00434  * address of the DNS server to be configured.
+00435  */
+00436 /*---------------------------------------------------------------------------*/
+00437 void
+00438 resolv_conf(u16_t *dnsserver)
+00439 {
+00440   if(resolv_conn != NULL) {
+00441     uip_udp_remove(resolv_conn);
+00442   }
+00443   
+00444   resolv_conn = uip_udp_new(dnsserver, HTONS(53));
+00445 }
+00446 /*---------------------------------------------------------------------------*/
+00447 /**
+00448  * Initalize the resolver.
+00449  */
+00450 /*---------------------------------------------------------------------------*/
+00451 void
+00452 resolv_init(void)
+00453 {
+00454   static u8_t i;
+00455   
+00456   for(i = 0; i < RESOLV_ENTRIES; ++i) {
+00457     names[i].state = STATE_DONE;
+00458   }
+00459 
+00460 }
+00461 /*---------------------------------------------------------------------------*/
+00462 
+00463 /** @} */
+00464 /** @} */
+